Can someone with beersmith or alike downsize DSGA to a final batch size of say 9-10L? With a run down of how much water to start with pre boil etc. I have quite large beer reserves atm and was going to start small 10L extract brews however I would really like to give this BIAB a crack.
Also if buying a bag or two of grain, what would be the more common ones that would definalty get used up(25kg bags). Basically a couple of common grains would be a good start.
I would just buy the brew's ingredients as you need them from one of the site sponsors above (possibly get enough for two batches or something). Get them to crack the grains too, it's free. Treat your first few brews as "experiments" - don't be hard on yourself about getting things perfect first time around, that's not important.
Since the good Doctor's recipe is for a 20L batch, make yours 10L - and
half all the ingredients. Easy as. I would forget the sparge this first time around since these small batches don't really gain much from sparging. You'll only have about 2kg of grain in the bag and since you started with 10L of mash water simply lifting the bag out and squeezing it over the pot liberates most of the goodness.
As far as volumes go (assuming you have a 15-19L pot) I would bring roughly 10L of water up to strike temperature, add your bag then grain, and insulate your pot.
The important thing here is that volumes are not really that important - the water is only there for the sugaz to go into at this stage.
So when you pull the bag out and squeeze it you'll probably end up with, say 8L of malty goodness because water will be left trapped in the grain. Squeeze it again - get all you can out.
Now you'll find that you have 8L of
too strong wort - probably somthing like 1.055 (DSGA is 1.047 OG) - so add about 4 or 5L of water to make it about 13L (yup, make it even weaker you're about to boil a lot of water off) and bring it to the boil ... add your hops (and set your phone's alarm to beep for the next addition etc).
If your boil was too hard-out, and you end up with under 10L ... simply add required boiling water at the end, just before you add your 1/4 whirlfloc tablet. It's better to boil too vigorously and add water later than to boil weakly and aim for 10L.
Above all, don't be too concerned with liquid volumes initially - after doing your first brew all the volume calculations will become crystal clear with
your set of gear. Write everything down and don't crack a beer until your wort is cooling!